Bug while "Undo your last item purchase"

I was down at approx 150 health when I backed, and immediately bought Brutalizer. When I was at full health, I Undid my purchase and bought Vampiric Scepter.

• It seems like my health got back to 150 and I had to wait in fountain again for full regain.

• Wouldve sucked with a Global Ult with this bug.

• Not sure if this is a bug with the Undo Feature, or specific with Twitch - Brutalizer - Vampiric Scepter purchase.

• Play Twitch -> Get low health

• Immediately when "B" and reached base, purchase Brutalizer

• When full health, Undo you're purchase and see what happens.

• gg

Got it at LoLRecorder too, if needed to spectate my champion.

http://www.twitch.tv/adaseif/b/585764441

Look at 10:50 - 11:05 (I'm playing the twitch - look at my health)